Pretty straightforward, you need to get pole position (first place) in qualifying in career mode.
I know I had a tough time doing this with the slower cars, but if anyone is struggling, my suggestion is to go to the Young Driver's Test's again and make sure you get 7-9 gold medals on the tests (7 gold lets you start with Sauber in career mode and 9 lets you start with Lotus). Once I got 9 I went with Lotus and got pole position and won the race in Melbourne. I also got the Rule the Roost achievement this way, which is to set the fastest time in every category in a long weekend, and I have been able to do it more than once.
So if you're struggling to do this with the weaker cars, I'd say go that route and go with either Sauber or Lotus. Everything was also done on Easy difficulty.